Some study designs are better than others for answering clinical questions, we can think of evidence being arranged in a hierarchy. The hierarchy is pyramid-shaped because as the study design becomes more rigorous, fewer of these types of studies are created. The most robust evidence, meta-analysis and systematic review, are at the very top of the evidence pyramid, because they are the most intensively reviewed.
"Evidence-based nursing (EBN) means using the best available evidence from research, along with patient preferences and clinical experience, when making nursing decisions."
Cullum N. (2000) Users' guides to the nursing literature: an introduction. Evidence Based Nursing. Jul;3(3):71-2. doi:10.1136/ebn.3.3.71
"An ongoing process by which evidence, nursing theory and the practitioners’ clinical expertise are critically evaluated and considered, in conjunction with patient involvement, to provide delivery of optimum nursing care for the individual."
Scott, K. & McSherry, R. "Evidence Based Nursing: clarifying the concepts for nurses in practice." Journal of Clinical Nursing 2009; 18(8): 1085-95.
Steps in Evidence Based Practice are:
Authors of a systematic review;
A meta-analysis is a systematic review that combines all the results of all the studies into a single statistical analysis of results.
Evidence summaries & evidence guidelines
Evidence is not always available via the resources and search strategies above. Instead, searching the primary literature may be required. It is possible to use specific search strategies in PubMed MEDLINE and CINAHL to achieve the highest possible level of evidence.
Different types of research studies are better suited to answering questions in various domains of inquiry. ALL research questions are best answered by well-done Meta-Analysis or Systematic Reviews; however, sometimes they are not available. In those cases, here are suggestions for types of single study by domain.
Domain— Single Study Types
Therapy— Randomized Controlled Trials (RCTs)
Prevention— Randomized Controlled Trials (RCTs) > cohort > case control > case series
Etiology/Harm— Cohort > case control > case series
Prognosis— Cohort (follow-up) > case control > case series
Diagnostic— Prospective, blind comparison to gold standard